"Om was first perceived by the ancient yogis of prehistory and is not the exclusive property of any religion or philosophy. It is not a sectarian mantra; it belongs to all without distinction or exclusion. Nor was it invented by those primal sages. Rather, it is swayambhu: self-begotten, self-existent and self-sufficient. It arises spontaneously within, from the Self. It does not need to be artificially implanted or empowered in us by any kind of initiation. This mantra is going on in every one of us, but as long as we are outward-turned we do not become aware of it.
During meditation, when we enter into our own depths, we become aware of Om, which has always been active within us. “What world does he who meditates on Om until the end of his life, win by That?
If he meditates on the Supreme Being with the Syllable Om, he becomes one with the light of the sun, he is led to the world of Brahman Who is higher than the highest life, That which is tranquil, unaging, immortal, fearless, and supreme” (Prashna Upanishad 5:1, 5, 7)."